Posted
by
ScuttleMonkey
on Wednesday April 25, 2007 @03:17PM
from the mash-downs dept.

Roland Piquepaille writes "What happens when you compress water in a nano-sized space? According to Georgia Tech physicists, water starts to behave like a solid. "The confined water film behaves like a solid in the vertical direction by forming layers parallel to the confining surface, while maintaining it's liquidity in the horizontal direction where it can flow out," said one of the researchers. "Water is a wonderful lubricant, but it flows too easily for many applications. At the one nanometer scale, water is a viscous fluid and could be a much better lubricant," added another one."

Well, you're partially right. The liquid water on frozen water is indeed very slippery. This is what allows ice skaters to skate, the blade glides along a thin film of liquid water. Frozen water on its own, however is not that slick.

Of course, PV=nRT is the ideal gas law, but there is a similar relationship for monolayers -(pi)A = nRT - a 2D analog of the ideal gas law for a layer one molecule thick which is often a liquid on another liquid or on a solid. This is when the monolayer is sparse enough that it acts like a gas, even though it may be comprised of molecules which are liquid at that temperature. Pi in the formula is the film pressure and A is the area. This is not really related to the phenomena described in TFA.

From what I can tell, F@H touched on this [stanford.edu] a while ago. I was reading the PS3 F@H articles, browsing through the "what good does F@H do?" and the "F@H is just a feel-good project" comments and looking at the results page [stanford.edu] when I stumbled across the above PDF and thought "Hey, that looks like something slashdot just reported on."

They did experiment with a Molecular Iamge PicoPlus AFM with the funny sound proof box and rubber bands, if you saw such a system you will know what I mean. The tip they used had a stiff cantilever and was "likely to be oxidized". They carefully controlled the sample surface and make it perpendicular to the tip. And they did the experiment on three surface, mica, soda lime untreated glass and highly oriented hydrophobic graphite.

And the result is hydrophilic surfaces showed increased viscosity and the hydrophobic surface showed no change.

Yes, liquid water under pressure at room temperature will indeed solidify. You need a hell of a lot of pressure, and the crystal form will be one of the other 12 known forms of ice, not the familiar ice(I) we know and love. In this case, it's actually ice(VII), a high pressure form consisting of two interpenetrating cubic lattices. The interpenetrating lattices allow more water to squeeze into a smaller space than in the liquid.
Water is a truly unique substance, from a physical chemistry standpoint. It often acts in ways that go against your physical intuition about how stuff should act. The obvious example everyone knows is the fact that the solid form is less dense than the liquid (so that ice floats), but there are many others. Lots of good reliable info here:
http://www.lsbu.ac.uk/water/ [lsbu.ac.uk]

well, my reply was just me teasing, but the thing that makes this unintuitive is that water as a solid is not more dense, so one wouldn't necessarily expect water that's been condensed to act like solid water, and as a matter of fact there had been studies that it didn't:

In its bulk liquid form, water is a disordered medium that flows very readily. When most substances are compressed into a solid, their density increases. But water is different; when it becomes ice, it becomes less dense. For this reason, many scientists reasoned that when water is compressed (as it is in a nanometer-sized channel), it should maintain its liquid properties and shouldn't exhibit properties that are akin to a solid. Several earlier studies came to that very conclusion - that water confined in a nano-space behaves just like water does in the macro world. Consequently, a number of scientists considered the case to be closed....
So why did Riedo and Landman's results differ from their peers? According to Landman, most previous studies on confined water were limited by technology at the time and could not directly measure the behavior in the last two nanometers. Instead they had to measure other properties and infer the forces acting in films of one nanometer thickness or less.